JPWO2008001662A1 - Optical member and optical apparatus provided with the same - Google Patents

Abstract

The present invention relates to an optical member and an optical device including the same. In particular, the present invention relates to an optical member having an antireflection concavo-convex structure formed on a surface for suppressing reflection of incident light, and an optical device including the same. An antireflection structure having excellent environmental resistance is provided. The optical member (antireflection structure) (1) includes an optical member body (10) and a protective film (20) that covers the surface (10a) of the optical member body (10) and transmits incident light. Yes. On the surface (10a) of the optical member body (10), a plurality of fine convex portions (12) are arranged, and an antireflection concavo-convex structure (11) that suppresses reflection of incident light is formed.

Description

  The present invention relates to an optical member and an optical device including the same. In particular, the present invention relates to an optical member having an antireflection concavo-convex structure formed on a surface for suppressing reflection of incident light, and an optical device including the same.

  In recent years, various optical elements in which antireflection treatment for suppressing light reflection is performed on the surface have been proposed. As the antireflection treatment, for example, a multilayer formed by alternately laminating a film having a relatively low refractive index (low refractive index film) or a film having a low refractive index and a film having a relatively high refractive index (high refractive index film). A treatment for forming an antireflection multilayer film composed of a film or the like on the surface (for example, Patent Document 1).

  However, the low refractive index film and the antireflection multilayer film require complicated processes such as a vapor deposition process and a sputtering process in forming the low refractive index film and the antireflection multilayer film. For this reason, there are problems that productivity is low and production cost is high. In addition, an antireflection film composed of a low refractive index film or a multilayer film also has a problem that its reflection suppression characteristics are highly wavelength dependent and incident angle dependent.

In view of such a problem, as an antireflection treatment with relatively small incident angle dependency and wavelength dependency of the reflection suppression characteristic, for example, the surface of the optical member has a fine structure (for example, a regular structure with a pitch less than the wavelength of incident light). A fine structure composed of linear recesses or convex protrusions arranged in a row, a fine structure composed of regularly arranged cone-shaped or columnar concave portions or protrusions, etc. Hereinafter, a plurality of such fine structures are arranged. There has been proposed a process for forming an anti-reflective uneven structure: SWS (Subwavelength Structured Surface) ”(for example, Non-Patent Documents 1 and 2). By forming the SWS on the surface, a rapid refractive index change at the interface is suppressed, and a gentle refractive index distribution can be formed at the interface. For this reason, according to the processing described in Patent Documents 1 and 2, a high reflection suppression effect can be obtained.
JP 2001-127852 A Daniel H. Lagunin (Daniel H. Raguin) By Michael Morris, “Analysis of anti-reflective-structurally-constrained-structure-contained-contained-frustration-structure-frustration-con- situation-of-reflective-structure-with-contrast-structure-with-contrast-structure-with-contrast-structure-with-constru- sion-f-consul-stu-

  However, the optical member having SWS formed on the surface (hereinafter sometimes referred to as “antireflection structure”) does not have sufficient environmental resistance (mechanical durability and chemical durability), and has a product life span. There is a problem of being short. In particular, when the antireflection structure is made of glass, chemical durability (water resistance, acid resistance, etc.) is inferior, and there is a possibility that white burn, blue burn, or the like may occur.

  This invention is made | formed in view of such a point, The place made into the objective is to provide the antireflection structure excellent in environmental resistance.

  In order to solve the above-mentioned object, an optical member according to the present invention includes an optical member body in which a plurality of fine convex portions or concave portions are arranged, and an antireflection uneven structure that suppresses reflection of incident light is formed on the surface. And a protective film that covers the surface of the optical member body and transmits incident light.

  Here, in this specification, “transmitting incident light” means not only transmitting incident light with a transmittance of substantially 100%, but also incident with a transmittance of a certain degree (for example, 10%) or more. The concept includes the case of transmitting light.

  An optical device according to the present invention includes the optical member according to the present invention.

  ADVANTAGE OF THE INVENTION According to this invention, the antireflection structure excellent in environmental resistance is realizable.

FIG. 1 is a plan view of an optical member (antireflection structure) 1 according to the first embodiment. FIG. 2 is a cross-sectional view of a portion cut out along a cut line II-II in FIG. FIG. 3 shows a period Λ: 300 nm, a refractive index of the optical member body 10 at a wavelength of 589 nm: 2.00136, a refractive index of the protective film 20 at a wavelength of 589 nm: 1.37986, t ₁ : 150 nm, t ₂ : 110 nm, a convex portion. 12 is a graph showing the correlation between the reflectance of the optical member 1 with respect to incident light with an incident angle of 0 ° and the wavelength of incident light when the diameter f of the top of 12 is 90.5 nm. FIG. 4 is a graph showing the correlation between the incident angle of incident light (wavelength: 589 nm) and the reflectance under the same conditions as in FIG. FIG. 5 shows a period Λ: 300 nm, a refractive index of the optical member body 10 at a wavelength of 589 nm: 2.00136, a refractive index of the protective film 20 at a wavelength of 589 nm: 1.37986, t ₁ : 150 nm, t ₂ : 140 nm, a convex portion. 12 is a graph showing the correlation between the reflectance of the optical member 1 with respect to incident light with an incident angle of 0 ° and the wavelength of incident light when the diameter f of the top of 12 is 135 nm. FIG. 6 is a graph showing the correlation between the incident angle of incident light (wavelength: 589 nm) and the reflectance under the same conditions as in FIG. FIG. 7 is a cross-sectional view of the optical member 2 according to the first modification. FIG. 8 is a plan view of the optical member 3 according to the second embodiment. FIG. 9 is a cross-sectional view of a portion cut out by a cut line IX-IX in FIG. In FIG. 10, the period Λ: 300 nm, the refractive index of the optical member body 10 at a wavelength of 589 nm: 1.51674, the refractive index of the protective film 20 at a wavelength of 589 nm: 1.10000, t ₁ : 150 nm, t ₂ : 40 nm, convex FIG. 7 is a graph showing the correlation between the reflectance of the optical member 3 and the wavelength of incident light with respect to incident light with an incident angle of 0 ° when the shape of the portion 12 is set to conform to y = −ax ² (a is an arbitrary constant). is there. FIG. 11 is a graph showing the correlation between the incident angle of incident light (wavelength: 589 nm) and the reflectance under the same conditions as in FIG. FIG. 12 is a cross-sectional view of the optical member 4 according to the second modification. FIG. 13 shows a period Λ: 300 nm, a refractive index of the optical member body 10 at a wavelength of 589 nm: 2.00136, a refractive index of the protective film 20 at a wavelength of 589 nm: 1.49169, t ₁ : 300 nm, t ₂ : 89 nm, t _3. : 243 nm, the reflectance of the optical member 4 with respect to the incident light with an incident angle of 0 ° and the wavelength of the incident light when the shape of the convex portion 12 is along y = −ax ² (a is an arbitrary constant) It is a graph showing a correlation. FIG. 14 is a graph showing the correlation between the incident angle of incident light (wavelength: 589 nm) and the reflectance under the same conditions as in FIG. FIG. 15 is a diagram illustrating a configuration of a main part of the imaging device 5 according to the third embodiment. FIG. 16 is a perspective view of the lens barrel 31. FIG. 17 is an enlarged cross-sectional view of a part of the lens barrel 31. FIG. 18 is a diagram illustrating a configuration of a main part of the optical pickup device 6 according to the fourth embodiment. FIG. 19 is a cross-sectional view of the objective lens 46.

Explanation of symbols

1, 2, 3, 4 Optical member 5 Imaging device 6 Optical pickup device 10 Optical member body 11, 36, 49 Anti-reflection concavo-convex structure (SWS)
DESCRIPTION OF SYMBOLS 12 Convex part 20,38,51a, 51b Protective film 30 Lens barrel unit 31 Lens barrel 32 Imaging optical system 33 Apparatus main body 34 Imaging element 35 Lens barrel main body 37 Linear convex part 41 Laser light source 42 Collimator 43 Beam splitter 45 Detector 46 Objective lens 47 Information recording medium 47a Information recording surface 48 Lens body 50 Conical convex portion

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
FIG. 1 is a plan view of an optical member (antireflection structure) 1 according to the first embodiment.

  FIG. 2 is a cross-sectional view of a portion cut out along a cut line II-II in FIG.

  The optical member 1 according to the first embodiment includes a flat plate-like optical member body 10 that is light transmissive (transmits incident light) and a light-transmissive protective film 20 that transmits incident light. . On the surface 10 a of the optical member body 10, a plurality of fine convex portions 12 are arranged, and an antireflection uneven structure (hereinafter sometimes referred to as “SWS”) 11 that suppresses reflection of incident light is formed. ing. The antireflection concavo-convex structure 11 is not particularly limited as long as it has a shape that smoothes the refractive index change in the vicinity of the surface 10 a of the optical member body 10. For example, the convex portion 12 may have a conical shape, a pyramid shape, a columnar shape, a prism shape, a truncated cone shape, a dome shape, or a truncated pyramid shape. Further, the antireflection concavo-convex structure 11 may be configured by arranging a plurality of conical, pyramidal, cylindrical, prismatic, truncated cone, dome-shaped or truncated pyramidal recesses, or lines extending in parallel to each other. You may comprise a row | line | column convex part or a recessed part.

  The surface 10 a on which the SWS 11 is formed is covered with a protective film 20. Therefore, high environmental resistance of the optical member 1 can be realized. When the protective film 20 is not present, the fine convex portion 12 is very easily deformed / damaged by colliding with other members or the like. By covering the fine convex portion 12 with the protective film 20, Deformation and breakage of the convex portion 12 when colliding with other members and the like can be effectively suppressed. As a result, high mechanical durability can be realized.

  In addition, for example, by making the protective film 20 higher in chemical durability than the optical member main body 10, chemical modification (discoloration or the like) of the optical member 1 can be effectively suppressed, and mechanical durability is improved. It is possible to realize the optical member 1 that is excellent in properties and chemical durability. In particular, when the optical member main body 10 is made of glass, such as burns, which easily undergoes chemical modification, it is preferable to form a protective film 20 made of a resin having a relatively high chemical durability on the surface 10a. . By doing so, the glass-made optical member main body 10 can be shielded from outside air (for example, oxygen, moisture, etc.), and chemical modification of the optical member main body 10 can be effectively suppressed. Therefore, the lifetime of the optical member 1 can be made relatively long. In the present specification, “high chemical durability” means high water resistance and / or acid resistance.

Moreover, the reflectance of the optical member 1 can be lowered by setting the refractive index at the wavelength of the incident light of the protective film 20 to be lower than the refractive index of the optical member body 10. For example, if the reflectance at the surface of the high refractive index of the optical member to R _1, the surface of the optical member in the case of forming a low refractive index layer having a lower refractive index than the refractive index of the optical member on the surface of the optical member The total reflectance R ₂ of the reflectance and the reflectance at the surface of the low refractive index layer is smaller than R ₁ . That is, by providing a layer having a refractive index lower than that of the optical member on the surface of the optical member, the total reflectance generated from the optical member can be reduced. And this reflectance reduction effect is the number of layers of the low refractive index layer laminated | stacked on the surface of an optical member (however, it sets so that the refractive index of a low refractive index layer may become low, so that it leaves | separates from the optical member main body 10). The larger the is, the larger it becomes. Now, in this Embodiment 1, SWS11 is formed in the surface 10a of the optical member main body 10, and also the protective film 20 is formed so that the surface 10a may be covered. The effective refractive index of the surface layer portion where the SWS 11 is formed is intermediate between the refractive index of the material itself constituting the optical member body 10 and the refractive index of the material of the protective film 20 itself. Therefore, as in the first embodiment, the SWS 11 is formed on the surface 10a, and the protective film 20 having a refractive index lower than the refractive index of the optical member body 10 is provided on the surface 10a. In addition, a layer having a lower refractive index than that of the optical member main body 10 (surface layer portion layer on which the SWS 11 is formed) is formed, and a layer having a lower refractive index than that of the layer (SWS 11). It is possible to form a state in which a portion that is formed only by the protective layer 20 is formed. As a result, the reflectance of the optical member 1 can be further reduced as compared with the case where the SWS 11 is formed on the surface 10 a and the protective film 20 is not formed, or the case where only the protective film 20 is formed without forming the SWS 11.

  Further, the protective film 20 has a thickness such that the phase of the reflected light on the surface 20a of the protective film 20 and the phase of the reflected light on the surface 10a of the optical member body 10 are shifted by half the wavelength of the incident light. Is preferred. Specifically, the substantial optical path difference between the reflected light on the surface 10a of the optical member body 10 and the reflected light on the surface 20a of the protective film 20 is shifted by 1/2 of the wavelength of the incident light. It is preferable to set so. By doing so, the reflected light on the surface 20a of the protective film 20 and the reflected light on the surface 10a of the optical member body 10 can be interfered and weakened. As a result, the reflectance of the optical member 1 can be further reduced. In this case, it is particularly preferable that the intensity of the reflected light generated on the surface 10a of the optical member body 10 is substantially equal to the intensity of the reflected light generated on the surface 20a of the protective film 20 by changing the shape of the antireflection concavo-convex structure 11. preferable. By doing so, it is possible to prevent substantially no reflected light. That is, a non-reflective structure can be realized.

  Further, by adjusting the film thickness of the protective film 20, it is possible to selectively reduce the reflectance at a certain wavelength or to reduce the wavelength dependency.

  Hereinafter, the specific configuration of the optical member 1 according to the first embodiment will be described in more detail with reference to FIGS. 1 and 2.

In the first embodiment, the optical member body 10 is substantially made of glass, and an antireflection concavo-convex structure 11 is formed on the surface 10a thereof. The antireflection concavo-convex structure 11 includes a plurality of columnar convex portions 12 regularly arranged. More specifically, in the first embodiment, the plurality of convex portions 12 have a period (less than the wavelength of the incident light (specifically, the shortest wavelength of the incident light when the incident light is not a single wavelength)) ( They are arranged in a matrix (square arrangement) spaced apart from each other by (pitch) Λ. The height t ₁ of the convex portion 12 is 0.4 times or more of the wavelength of the incident light (specifically, when the incident light is not light of a single wavelength, 0.4 times or more of the longest wavelength of the incident light) ) Is set. For this reason, a layer whose refractive index gradually changes is formed on the surface portion of the surface 10a, and reflection of incident light incident on the surface 10a via the protective film 20 is effectively suppressed.

  In addition, even if it is a case where the convex part 12 is columnar like this Embodiment 1, the effective refractive index of the surface layer part in which the convex part 12 exists can be reduced by providing the convex part 12. FIG. Therefore, the reflection of incident light can be effectively reduced.

  On this surface 10a, a protective film 20 substantially made of a resin is formed so as to cover the surface 10a. Specifically, in the first embodiment, the protective film 20 fills the concave portions between the plurality of convex portions 12 arranged, and the surface 20a opposite to the optical member body 10 side of the protective film 20 is a smooth surface (unevenness). A smooth surface or the like in the first embodiment. For this reason, the convex part 12 is protected from the impact and vibration from the outside by this protective film 20, and the deformation | transformation and damage of the convex part 12 are suppressed effectively. Therefore, high mechanical durability can be realized.

  By the way, in general, glass has low chemical durability (water resistance and acid resistance), and when the glass material is exposed, white burn or blue burn is generated. On the other hand, since resin has higher chemical durability than glass, chemical modification of optical member main body 10 substantially made of glass is achieved by covering optical member 10 with protective film 20 made substantially of resin. (Discoloration etc.) can be effectively suppressed.

  In the first embodiment, the protective film 20 has a refractive index at a wavelength of incident light lower than that of the optical member body 10. For this reason, it will be in the state where two layers whose refractive index is lower than optical member main part 10 are laminated on surface 10a of optical member main part 10 as mentioned above. Therefore, the reflectance of the optical member 1 can be effectively reduced.

Distance from the top of the convex portion 12 to the surface 20a (in this specification, thickness and defining this distance protective membrane 20) t ₂ is the reflectance of the optical member 1, the wavelength of the reflectance of the optical member 1 Correlate with both dependencies. For example, the incident light may be light of a single wavelength, the thickness t ₂ of the protective layer 20, the reflected light generated on the surface 10a of the optical member body 10 phase and the reflected light generated by the surface 20a of the protective film 20 By setting the difference from the phase to be half (1/2) the wavelength of the incident light, the reflected light generated on the surface 10a and the reflected light generated on the surface 20a can be interfered and weakened. Therefore, by setting the thickness t ₂ of the thus protective layer 20, it is possible to reduce the reflectance of the optical member 1 for incident light of a certain wavelength more effectively. In this case, the height t ₁ of the convex portion 12, and particularly preferably the intensity of the reflected light generated by the reflection light intensity and the surface 20a occurring at the surface 10a such that substantially equal. By doing so, it becomes possible to make the reflectance of the optical member 1 substantially zero.

However, if you set the thickness t ₂ of such protection film 20, resulting in the surface 20a of the phase and the protective film 20 of the reflected light generated on the surface 10a of the optical member body 10 with respect to incident light of another wavelength Since the difference from the phase of the reflected light does not become half (1/2) of the wavelength of the incident light, the wavelength dependence of the reflectance of the optical member 1 becomes relatively large.

Hereinafter, by changing the conditions of the film thickness t _2, etc. of the protective film 20, more specifically described by way of a specific example that it is possible to change the reflectance and the wavelength dependence of the optical member 1.

FIG. 3 shows a period Λ: 300 nm, a refractive index of the optical member body 10 at a wavelength of 589 nm: 2.00136, a refractive index of the protective film 20 at a wavelength of 589 nm: 1.37986, t ₁ : 150 nm, t ₂ : 110 nm, a convex portion. 12 is a graph showing the correlation between the reflectance of the optical member 1 with respect to incident light with an incident angle of 0 ° and the wavelength of incident light when the diameter f of the top of 12 is 90.5 nm. The dispersion of the protective film 20 is defined by the following mathematical formula (1). Further, the dispersion of the optical member body 10 is defined by the following mathematical formula (2).
n ² −1 = K ₁ λ ² / (λ ² −L ₁ ) + K ₂ λ ² / (λ ² −L ₂ ) + K ₃ λ ² / (λ ² −L ₃ ) (1)
However,
K ₁ = 0.487555108,
K ₂ = 0.398775031,
K ₃ = 2.3120353,
L ₁ = 0.00600069867,
L ₂ = 0.00895188847,
L ₃ = 566.135559,
It is.
n ² = a ₀ + a ₁ λ ² ++ a ₂ λ ⁻² + a ₃ λ ⁻⁴ + a ₄ λ ⁻⁶ + a ₅ λ ⁻⁸ (2)
However,
a ₀ = 3.778725,
a ₁ = −0.020974414,
a ₂ = 0.0592558017,
a ₃ = 0.0079700797,
a ₄ = −0.00070884578,
a ₅ = 7.9345324e-005,
It is.

  FIG. 4 is a graph showing the correlation between the incident angle of incident light (wavelength: 589 nm) and the reflectance under the same conditions as in FIG.

FIG. 5 shows a period Λ: 300 nm, a refractive index of the optical member body 10 at a wavelength of 589 nm: 2.00136, a refractive index of the protective film 20 at a wavelength of 589 nm: 1.37986, t ₁ : 150 nm, t ₂ : 140 nm, a convex portion. 12 is a graph showing the correlation between the reflectance of the optical member 1 with respect to incident light with an incident angle of 0 ° and the wavelength of incident light when the diameter f of the top of 12 is 135 nm. The dispersion of the protective film 20 is defined by the above mathematical formula (1). Further, the dispersion of the optical member body 10 is defined by the above mathematical formula (2).

  FIG. 6 is a graph showing the correlation between the incident angle of incident light (wavelength: 589 nm) and the reflectance under the same conditions as in FIG.

3 to 6, A indicates the reflectance of the optical member 1 of the first embodiment. B shows the reflectance when the SWS 11 is not provided and the protective film 20 is formed on the flat surface 10a. C indicates the reflectance when the protective film 20 is not provided. Also, D is, without providing the protective film 20, and shows the reflectance in the case of half the height t ₁ of the convex portion 12.

  Here, the conditions of the graph (A) shown in FIGS. 3 and 4 are the phase of the reflected light generated on the surface 10a of the optical member body 10 and the surface 20a of the protective film 20 when incident light having a wavelength of 589 nm is incident. The difference from the phase of the generated reflected light is half (1/2) the wavelength of the incident light, and the intensity of the reflected light generated on the surface 10a and the reflected light generated on the surface 20a in that case is substantially the same. It is a condition. By setting such conditions, as shown in FIGS. 3 and 4, reflection of vertical incident light having a wavelength of 589 nm (incident light having an incident angle of 0 °) can be suppressed almost completely.

  In addition, as shown in FIG. 4, by providing the protective film 20, it is possible to effectively suppress the reflection of incident light having a particularly small incident angle, compared to the case where the protective film 20 is not provided (C, D). . However, as shown in FIG. 3, the wavelength dependency of the reflectance tends to be larger than when the protective film 20 is not provided (in the case of C or D).

  On the other hand, under the conditions of the graph (A) shown in FIGS. 5 and 6, unlike the case shown in FIG. 3 and the like, the reflectance of the optical member 1 is substantially zero as shown in FIG. Although no particular wavelength appears, the wavelength dependence of the reflectance can be further reduced. 5 and 6 that the wavelength dependency of the reflectance can be further reduced as compared with the case where the protective film 20 is not provided.

  As described above, in the first embodiment, an example of a preferable embodiment in which the present invention is implemented is described by taking the case where the optical member main body 10 transmits incident light as an example, but the present invention is limited to this configuration. It is not a thing. For example, the optical member body 10 may be a so-called black body that absorbs incident light. Even in that case, the environmental resistance can be improved by providing the protective film 20. In addition, the light reflectance can be more effectively reduced.

  In the first embodiment, the example in which the convex portions 12 are squarely arranged in a matrix has been described. However, the arrangement of the convex portions 12 is not particularly limited to this. For example, a triangular lattice shape (delta shape) ) May be arranged. The arrangement of the protrusions 12 is not particularly limited as long as a gentle refractive index change occurs in the surface layer portion where the protrusions 12 (antireflection uneven structure 11) are formed.

  In the first embodiment, the optical member 1 on which the surface on which the SWS 11 is formed is a flat surface has been described as an example. However, as shown in the following embodiment, the shape of the surface on which the SWS 11 is provided is particularly limited. The shape of the optical member according to the present invention is not particularly limited.

(Modification 1)
FIG. 7 is a cross-sectional view of the optical member 2 according to the first modification.

  The optical member 2 according to Modification 1 has the same configuration except for the configuration of the optical member 1 according to Embodiment 1 and the protective film 20. Here, the configuration of the protective film 20 in Modification 1 will be described in detail. In the description of the first modification, components having substantially the same function will be described with reference numerals common to the first embodiment, and description thereof will be omitted.

  In the first embodiment, the protective film 20 is relatively thick and fills the concave portions formed between the plurality of convex portions 12 and is formed so that the surface 20a becomes a smooth surface (for example, a smooth surface). Has been. However, the present invention is not limited to this configuration. For example, as in Modification 2, the protective film 20 may be relatively thin and formed in a shape along the antireflection uneven structure 11. . That is, unevenness corresponding to the antireflection uneven structure 11 may be formed on the surface 20a. Even in this case, high chemical durability can be realized as in the case of the first embodiment. Further, higher mechanical durability can be realized than when the protective film 20 is not provided.

  Further, as in the case of Example 1 described above, the layer thickness of the protective film 20 and the shape of the projections 12 are appropriately adjusted to further reduce the reflectance and reduce the wavelength dependence of the reflectance. Can be planned.

(Embodiment 2)
FIG. 8 is a plan view of the optical member 3 according to the second embodiment.

  FIG. 9 is a cross-sectional view of a portion cut out by a cut line IX-IX in FIG.

  The optical member 3 according to Embodiment 2 has the same configuration except for the shape of the optical member 1 according to Embodiment 1 and the antireflection uneven structure 11. Here, the shape of the antireflection concavo-convex structure 11 in Embodiment 2 will be described in detail. In the description of the second embodiment, components having substantially the same function are described with reference numerals common to the first embodiment, and the description thereof is omitted.

  As shown in FIGS. 8 and 9, in the second embodiment, the antireflection concavo-convex structure (SWS) 11 is constituted by a plurality of dome-shaped convex portions 12 arranged densely in a matrix. As in the second embodiment, the antireflection concavo-convex structure 11 is configured by the plurality of dome-shaped convex portions 12, so that the antireflection concavo-convex structure 11 is configured by the plurality of columnar convex portions 12 in the surface layer portion. The refractive index change can be made smoother. Further, incident light is irregularly reflected on the surface 10a. Therefore, the reflectance at the surface 10a can be further reduced.

  Moreover, the wavelength dependence of the reflectance of the optical member 3 can be further reduced. Furthermore, the incident angle dependency of the reflectance of the optical member 3 can be further reduced, and a high reflection suppressing effect can be realized even for incident light having a relatively large incident angle.

  In the second embodiment, the reflectance on the surface 10a of the optical member body 10 correlates with the height of the convex portion 12 formed on the surface 10a. Specifically, the reflectance decreases as the height of the convex portion 12 increases, and conversely, the reflectance tends to increase as the height of the convex portion 12 decreases. As described above, by providing the protective film 20 made of a low refractive index material, the reflectivity of the optical member 3 (“reflectance of the optical member” is emitted from the surface 20a with respect to the intensity of light incident on the surface 10a. The intensity of the reflected light (which is the intensity of the combined reflected light generated on the surface 10a and the reflected light generated on the surface 20a) can be reduced. It is possible to achieve a desired low reflectance even when the value is lowered. That is, by providing the protective film 20, the height of the convex portion 12 can be made relatively low, and the optical member 3 can be easily manufactured.

  Hereinafter, the reflection suppression effect of the optical member 3 according to the second embodiment will be specifically described with reference to further specific examples.

In FIG. 10, the period Λ: 300 nm, the refractive index of the optical member body 10 at a wavelength of 589 nm: 1.51674, the refractive index of the protective film 20 at a wavelength of 589 nm: 1.10000, t ₁ : 150 nm, t ₂ : 40 nm, convex FIG. 7 is a graph showing the correlation between the reflectance of the optical member 3 and the wavelength of incident light with respect to incident light with an incident angle of 0 ° when the shape of the portion 12 is set to conform to y = −ax ² (a is an arbitrary constant). is there. However, the y axis extends in the normal direction of the base surface of the surface 10a, and the x axis extends in a direction perpendicular to the y axis in a cross section passing through the center of the convex portion 12. Further, the wavelength dependency of the refractive index of the protective film 20 is not assumed.

  FIG. 11 is a graph showing the correlation between the incident angle of incident light (wavelength: 589 nm) and the reflectance under the same conditions as in FIG.

10 and 11, A indicates the reflectance of the optical member 3 of the second embodiment. B shows the reflectance when the SWS 11 is not provided and the protective film 20 is formed on the flat surface 10a. C indicates the reflectance when the protective film 20 is not provided. Also, D is, without providing the protective film 20, and shows the reflectance in the case of half the height t ₁ of the convex portion 12.

  As shown in FIG. 10, the reflectance of the optical member 3 and its wavelength dependency can be more effectively reduced by adopting the configuration of the second embodiment. Moreover, as shown in FIG. 11, the incident angle dependence of the reflectance of the optical member 3 can be further reduced, and the reflectance for incident light having a relatively large incident angle can also be effectively reduced.

(Modification 2)
FIG. 12 is a cross-sectional view of the optical member 4 according to the second modification.

FIG. 13 shows a period Λ: 300 nm, a refractive index of the optical member body 10 at a wavelength of 589 nm: 2.00136, a refractive index of the protective film 20 at a wavelength of 589 nm: 1.49169, t ₁ : 300 nm, t ₂ : 89 nm, t _3. : 243 nm, the reflectance of the optical member 4 with respect to the incident light with an incident angle of 0 ° and the wavelength of the incident light when the shape of the convex portion 12 is along y = −ax ² (a is an arbitrary constant) It is a graph showing a correlation. The dispersion of the protective film 20 is defined by the following mathematical formula (3). Further, the dispersion of the optical member body 10 is defined by the following mathematical formula (4).
n ² = a ₀ + a ₁ λ ² +++ a ₂ λ ⁻² + a ₃ λ ⁻⁴ + a ₄ λ ⁻⁶ + a ₅ λ ⁻⁸ (3)
However,
a ₀ = 2.1864582,
a ₁ = −0.00024475348,
a ₂ = 0.0145155787,
a ₃ = −0.000443297981,
a ₄ = 7.7664259e-005,
a ₅ = −2.9936382e-006,
It is.
n ² = a ₀ + a ₁ λ ² ++ a ₂ λ ⁻² + a ₃ λ ⁻⁴ + a ₄ λ ⁻⁶ + a ₅ λ ⁻⁸ (4)
However,
a ₀ = 3.778725,
a ₁ = −0.020974414,
a ₂ = 0.0592558017,
a ₃ = 0.0079700797,
a ₄ = −0.00070884578,
a ₅ = 7.9345324e-005,
It is.

  FIG. 14 is a graph showing the correlation between the incident angle of incident light (wavelength: 589 nm) and the reflectance under the same conditions as in FIG.

In FIGS. 13 and 14, A represents the reflectance of the optical member 4 of the second modification. B shows the reflectance when the SWS 11 is not provided and the protective film 20 is formed on the flat surface 10a. C indicates the reflectance when the protective film 20 is not provided. Also, D is, without providing the protective film 20, and shows the reflectance in the case of half the height t ₁ of the convex portion 12.

  The optical member 4 according to the second modification has the same configuration except for the configuration of the optical member 3 and the protective film 20 according to the second embodiment. Here, the configuration of the protective film 20 in Modification 2 will be described in detail. In the description of the second modification, components having substantially the same function will be described with reference numerals common to the first and second embodiments, and description thereof will be omitted.

  In the second embodiment, the protective film 20 is relatively thick and fills the concave portions formed between the plurality of convex portions 12 and is formed so that the surface 20a becomes a smooth surface (for example, a smooth surface). Has been. However, the present invention is not limited to this configuration. For example, as in Modification 2, the protective film 20 may be relatively thin and formed in a shape along the antireflection uneven structure 11. . That is, unevenness corresponding to the antireflection uneven structure 11 may be formed on the surface 20a. Even in this case, high chemical durability can be realized as in the case of the second embodiment. Further, higher mechanical durability can be realized than when the protective film 20 is not provided.

  Further, as shown in FIGS. 13 and 14, as in the case of the first embodiment, the reflectance can be further effectively reduced by appropriately adjusting the layer thickness of the protective film 20 and the shape of the convex portion 12. In addition, the wavelength dependence of the reflectance can be reduced.

  Next, an optical device using the optical member embodying the present invention will be described by taking Embodiments 3 and 4 as examples.

(Embodiment 3)
FIG. 15 is a diagram illustrating a configuration of a main part of the imaging device 5 according to the third embodiment.

  As illustrated in FIG. 15, the imaging apparatus 5 according to the third embodiment includes an apparatus main body 33, a lens barrel unit 30, and an imaging element 34. The lens barrel unit 30 includes a cylindrical (specifically cylindrical) lens barrel 31 and an imaging optical system 32 housed inside the lens barrel 31. The imaging optical system 32 is for imaging light incident on the lens barrel 31 from the image side (left side in FIG. 15). In the third embodiment, the imaging optical system 32 is specifically configured by a first lens 32a, a second lens 32b, and a third lens 32c. The lenses 32a to 32c constituting the imaging optical system 32 may be disposed on the optical axis so as not to be displaced. In addition, at least one of the lenses 32a to 32c is configured to be displaceable on the optical axis, and may be configured to be capable of focusing and zooming.

  The lens barrel unit 30 is attached to the apparatus main body 33. The lens barrel unit 30 may be detachable from the apparatus main body 33 or may be attached to the apparatus main body 33 so as not to be detached.

  The device body 33 is provided with an image sensor 34. The image sensor 34 is disposed on the optical axis of the imaging optical system 32. Specifically, the imaging element 34 has an imaging surface, and is arranged so that an optical image is formed on the imaging surface by the imaging optical system 32. The image sensor 34 has a function as a photodetector. Specifically, the image sensor 34 has a function of detecting an optical image formed on the optical image and outputting an electrical signal corresponding to the optical image. The image sensor 34 can be configured by, for example, a charge coupled device (CCD), a complementary metal-oxide semiconductor (COMS), or the like.

  In the third embodiment, the electrical signal output from the image sensor 34 is configured to be input and recorded in a recording device (not shown) (for example, a hard disk) housed in the apparatus main body 33.

  FIG. 16 is a perspective view of the lens barrel 31.

  FIG. 17 is an enlarged sectional view of a part of the lens barrel 31.

  In principle, the imaging optical system 32 is designed so that light incident on the imaging optical system 32 is imaged on the imaging surface of the imaging element 34. However, a part of the light incident on the imaging optical system 32, such as light having a maximum angle of view of the imaging optical system 32, is not directly imaged on the image sensor 34 but is incident on the inner peripheral surface of the lens barrel 31. Will be. For this reason, when the light reflectance of the inner peripheral surface of the lens barrel 31 is high, reflected light (stray light) is generated on the inner peripheral surface, which may cause ghost or flare.

  In the third embodiment, the lens barrel 31 includes a barrel main body 35 formed in a cylindrical shape and a protective film 38 that is formed so as to cover the inner peripheral surface of the barrel main body 35 and transmits visible light. It is comprised by. An antireflection concavo-convex structure (so-called SWS) 36 is formed over the entire inner peripheral surface of the lens barrel body 35. The antireflection concavo-convex structure 36 is formed by regularly arranging a plurality of fine linear protrusions 37 extending in parallel with each other in the extending direction of the lens barrel 31 along the circumferential surface. Specifically, the plurality of linear protrusions 37 are arranged at a pitch (pitch: distance between the apexes between adjacent linear protrusions 37) that is equal to or less than the wavelength of the light from the imaging optical system 32. Specifically, for example, when visible light (light having a wavelength of 400 nm or more and 700 nm or less) is incident on the imaging optical system 32, light (for example, the imaging element 34 has a wavelength of 450 nm) that suppresses reflection among the incident light. In the case where the following light is not detected, the light can be 450 nm or more), and the light is arranged at a pitch equal to or shorter than the wavelength of the shortest light.

  The lens barrel body 35 is configured to absorb light from the imaging optical system 32. Specifically, the lens barrel main body 35 is configured to include a light absorbing material (for example, a black dye or a black pigment). For this reason, the reflection of the incident light on the inner peripheral surface is effectively suppressed, and the incident light on the lens barrel 31 is absorbed by the barrel main body 35 with a high absorption rate. Therefore, generation of stray light due to reflected light or the like on the inner peripheral surface can be suppressed. As a result, the occurrence of ghosts and flares can be effectively suppressed, and the imaging device 5 having high optical performance can be realized.

  In the third embodiment, as shown in FIG. 17, the protective film 38 is formed on the antireflection concavo-convex structure 36 so as to cover the antireflection concavo-convex structure 36. As described above, high environmental resistance can be realized. Further, since the refractive index distribution can be made gentler in the surface layer portion near the inner peripheral surface of the lens barrel 31, the generation of reflected light in the lens barrel 31 can be more effectively suppressed. Therefore, higher optical performance of the imaging device 5 can be realized.

  In addition, it is preferable to form the inner peripheral surface of the lens barrel 31 on which the SWS 36 is formed as a rough surface from the viewpoint of realizing higher optical performance. By doing so, the incidence angle dependence of the reflectance on the inner peripheral surface can be further reduced, and the regular reflection component can be more effectively reduced.

(Embodiment 4)
FIG. 18 is a diagram illustrating a configuration of a main part of the optical pickup device 6 according to the fourth embodiment.

  FIG. 19 is a cross-sectional view of the objective lens 46.

  The optical pickup device 6 according to the fourth embodiment focuses information on the information recording surface 47a of an information recording medium (for example, an optical disc) 47 and detects reflected light on the information recording surface 47a to record information. The information recorded on the surface 47a can be read out.

  The optical pickup device 6 includes a laser light source 41, a collimator 42, a beam splitter 43, an objective lens 46 constituting an objective optical system, and a detector 45. The collimator 42 has a function of converting laser light emitted from the laser light source 41 into parallel light. The laser light converted into parallel light by the collimator 42 passes through the beam splitter 43 and enters the objective lens 46. The objective lens 46 is for focusing the laser beam on the information recording surface 47a of the information recording medium 47 provided with the laser beam. The laser beam focused by the objective lens 46 is reflected by the information recording surface 47a. The reflected light passes through the objective lens 46 and enters the beam splitter 43. The light is reflected by the reflecting surface provided on the beam splitter 43 and the reflected light is guided to the detector 45. The reflected light is detected by the detector 45, and data is read based on the detected reflected light.

  In the fourth embodiment, an example of the present invention will be described by taking an optical pickup device 6 of a type that focuses laser light on one type of information recording medium 47 as an example. A so-called compatible type capable of focusing laser light on each of the recording media 47 may be used.

  Incidentally, as described above, the laser light incident on the objective lens 46 passes through the objective lens 46. However, if antireflection processing is not performed on both lens surfaces of the objective lens 46, a part of the laser light is reflected on both lens surfaces of the objective lens 46. If a part of the laser beam is reflected on both lens surfaces of the objective lens 46, the amount of the laser beam detected by the detector 45 is decreased, so that the detection accuracy tends to be decreased. As a result, noise or the like may occur.

  In the fourth embodiment, the objective lens 46 includes a lens body 48 and protective films 51 a and 51 b provided on the lens surfaces of the lens body 48 so as to cover the lens surfaces. An antireflection concavo-convex structure 49 in which a plurality of fine cone-shaped convex portions 50 are regularly arranged is formed at least within the effective optical diameter of the lens surface 48a on the laser light source 41 side of the lens body 48. . Specifically, the plurality of cone-shaped convex portions 50 are arranged at a pitch (the distance between the apexes between the cone-shaped convex portions 50 located closest to each other) that is equal to or less than the wavelength of the laser light emitted from the laser light source 41. (For example, a square arrangement or a triangular lattice arrangement).

  Further, an antireflection concavo-convex structure 49 in which a plurality of fine cone-shaped convex portions 50 are regularly arranged is formed at least within the effective optical diameter of the lens surface 48b on the information recording medium 47 side of the lens body 48. Yes. Specifically, the plurality of cone-shaped convex portions 50 are arranged at a pitch (the distance between the apexes between the cone-shaped convex portions 50 located closest to each other) that is equal to or less than the wavelength of the laser light emitted from the laser light source 41. (For example, a square arrangement or a triangular lattice arrangement).

  For this reason, the reflection of the laser beam on both lens surfaces of the objective lens 46 can be suppressed. As a result, the amount of laser light detected by the detector 45 can be made relatively large, and the generation of noise can be effectively suppressed. Therefore, the optical pickup device 6 having high optical performance can be realized.

  In the fourth embodiment, protective films 51 a and 51 b are formed on each lens surface of the lens body 48 so as to cover the antireflection uneven structure 49. For this reason, as demonstrated in the said Embodiment 1, high environmental resistance and a higher reflection suppression effect are realizable. Therefore, the optical pickup device 6 having higher optical performance can be realized.

  As long as the pitch of the antireflection concavo-convex structure 49 is equal to or less than the wavelength of the laser beam within at least the optical effective diameter of the lens surfaces 48a and 46b, the pitch of the antireflection concavo-convex structure 49 is within the optical effective diameter of the lens surfaces 48a and 46b. May be substantially constant (i.e., may be periodic). In addition, the pitch of the antireflection concavo-convex structure 49 may be different from each other at various locations within the optical effective diameter. That is, the antireflection uneven structure 49 may be aperiodic. Generation of diffracted light on the lens surfaces 48a and 46b can be effectively suppressed by making the antireflection uneven structure 49 non-periodic.

  As described above, in the third and fourth embodiments, the imaging device and the optical pickup device have been described as examples of the optical device including the optical member according to the present invention. However, the present invention is not limited to the optical scanning device or the like. The present invention can also be applied to various optical devices.

  The optical member according to the present invention has an antireflection effect and high environmental resistance, and is useful as a lens barrel, an optical element represented by a lens, and the like. By using the optical member according to the present invention, various optical systems such as a high-quality imaging optical system, objective optical system, scanning optical system, and pickup optical system, lens barrel unit, optical pickup unit, and imaging unit An optical unit, an imaging device, an optical pickup device, an optical scanning device, and the like can be realized.

  The present invention relates to an optical member and an optical device including the same. In particular, the present invention relates to an optical member having an antireflection concavo-convex structure formed on a surface for suppressing reflection of incident light, and an optical device including the same.

  In recent years, various optical elements in which antireflection treatment for suppressing light reflection is performed on the surface have been proposed. As the antireflection treatment, for example, a multilayer formed by alternately laminating a film having a relatively low refractive index (low refractive index film) or a film having a low refractive index and a film having a relatively high refractive index (high refractive index film). A treatment for forming an antireflection multilayer film composed of a film or the like on the surface (for example, Patent Document 1).

  However, the low refractive index film and the antireflection multilayer film require complicated processes such as a vapor deposition process and a sputtering process in forming the low refractive index film and the antireflection multilayer film. For this reason, there are problems that productivity is low and production cost is high. In addition, an antireflection film composed of a low refractive index film or a multilayer film also has a problem that its reflection suppression characteristics are highly wavelength dependent and incident angle dependent.

In view of such a problem, as an antireflection treatment with relatively small incident angle dependency and wavelength dependency of the reflection suppression characteristic, for example, the surface of the optical member has a fine structure (for example, a regular structure with a pitch less than the wavelength of incident light). A fine structure composed of linear recesses or convex protrusions arranged in a row, a fine structure composed of regularly arranged cone-shaped or columnar concave portions or protrusions, etc. Hereinafter, a plurality of such fine structures are arranged. There has been proposed a process for forming an anti-reflective uneven structure: SWS (Subwavelength Structured Surface) ”(for example, Non-Patent Documents 1 and 2). By forming the SWS on the surface, a rapid refractive index change at the interface is suppressed, and a gentle refractive index distribution can be formed at the interface. For this reason, according to the processing described in Patent Documents 1 and 2, a high reflection suppression effect can be obtained.
JP 2001-127852 A Daniel H. Lagunin (Daniel H. Raguin) By Michael Morris, “Analysis of anti-reflective-structurally-constrained-structure-contained-contained-frustration-structure-frustration-con- situation-of-reflective-structure-with-contrast-structure-with-contrast-structure-with-contrast-structure-with-constru- sion-f-consul-stu-

  However, the optical member having SWS formed on the surface (hereinafter sometimes referred to as “antireflection structure”) does not have sufficient environmental resistance (mechanical durability and chemical durability), and has a product life span. There is a problem of being short. In particular, when the antireflection structure is made of glass, chemical durability (water resistance, acid resistance, etc.) is inferior, and there is a possibility that white burn, blue burn, or the like may occur.

  This invention is made | formed in view of such a point, The place made into the objective is to provide the antireflection structure excellent in environmental resistance.

  In order to solve the above-mentioned object, an optical member according to the present invention includes an optical member body in which a plurality of fine convex portions or concave portions are arranged, and an antireflection uneven structure that suppresses reflection of incident light is formed on the surface. And a protective film that covers the surface of the optical member body and transmits incident light.

  Here, in this specification, “transmitting incident light” means not only transmitting incident light with a transmittance of substantially 100%, but also incident with a transmittance of a certain degree (for example, 10%) or more. The concept includes the case of transmitting light.

  An optical device according to the present invention includes the optical member according to the present invention.

  ADVANTAGE OF THE INVENTION According to this invention, the antireflection structure excellent in environmental resistance is realizable.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
FIG. 1 is a plan view of an optical member (antireflection structure) 1 according to the first embodiment.

  FIG. 2 is a cross-sectional view of a portion cut out along a cut line II-II in FIG.

  The optical member 1 according to the first embodiment includes a flat plate-like optical member body 10 that is light transmissive (transmits incident light) and a light-transmissive protective film 20 that transmits incident light. . On the surface 10 a of the optical member body 10, a plurality of fine convex portions 12 are arranged, and an antireflection uneven structure (hereinafter sometimes referred to as “SWS”) 11 that suppresses reflection of incident light is formed. ing. The antireflection concavo-convex structure 11 is not particularly limited as long as it has a shape that smoothes the refractive index change in the vicinity of the surface 10 a of the optical member body 10. For example, the convex portion 12 may have a conical shape, a pyramid shape, a columnar shape, a prism shape, a truncated cone shape, a dome shape, or a truncated pyramid shape. Further, the antireflection concavo-convex structure 11 may be configured by arranging a plurality of conical, pyramidal, cylindrical, prismatic, truncated cone, dome-shaped or truncated pyramidal recesses, or lines extending in parallel to each other. You may comprise a row | line | column convex part or a recessed part.

  The surface 10 a on which the SWS 11 is formed is covered with a protective film 20. Therefore, high environmental resistance of the optical member 1 can be realized. When the protective film 20 is not present, the fine convex portion 12 is very easily deformed / damaged by colliding with other members or the like. By covering the fine convex portion 12 with the protective film 20, Deformation and breakage of the convex portion 12 when colliding with other members and the like can be effectively suppressed. As a result, high mechanical durability can be realized.

  In addition, for example, by making the protective film 20 higher in chemical durability than the optical member main body 10, chemical modification (discoloration or the like) of the optical member 1 can be effectively suppressed, and mechanical durability is improved. It is possible to realize the optical member 1 that is excellent in properties and chemical durability. In particular, when the optical member main body 10 is made of glass, such as burns, which easily undergoes chemical modification, it is preferable to form a protective film 20 made of a resin having a relatively high chemical durability on the surface 10a. . By doing so, the glass-made optical member main body 10 can be shielded from outside air (for example, oxygen, moisture, etc.), and chemical modification of the optical member main body 10 can be effectively suppressed. Therefore, the lifetime of the optical member 1 can be made relatively long. In the present specification, “high chemical durability” means high water resistance and / or acid resistance.

Moreover, the reflectance of the optical member 1 can be lowered by setting the refractive index at the wavelength of the incident light of the protective film 20 to be lower than the refractive index of the optical member body 10. For example, if the reflectance at the surface of the high refractive index of the optical member to R _1, the surface of the optical member in the case of forming a low refractive index layer having a lower refractive index than the refractive index of the optical member on the surface of the optical member The total reflectance R ₂ of the reflectance and the reflectance at the surface of the low refractive index layer is smaller than R ₁ . That is, by providing a layer having a refractive index lower than that of the optical member on the surface of the optical member, the total reflectance generated from the optical member can be reduced. And this reflectance reduction effect is the number of layers of the low refractive index layer laminated | stacked on the surface of an optical member (however, it sets so that the refractive index of a low refractive index layer may become low, so that it leaves | separates from the optical member main body 10). The larger the is, the larger it becomes. Now, in this Embodiment 1, SWS11 is formed in the surface 10a of the optical member main body 10, and also the protective film 20 is formed so that the surface 10a may be covered. The effective refractive index of the surface layer portion where the SWS 11 is formed is intermediate between the refractive index of the material itself constituting the optical member body 10 and the refractive index of the material of the protective film 20 itself. Therefore, as in the first embodiment, the SWS 11 is formed on the surface 10a, and the protective film 20 having a refractive index lower than the refractive index of the optical member body 10 is provided on the surface 10a. In addition, a layer having a lower refractive index than that of the optical member main body 10 (surface layer portion layer on which the SWS 11 is formed) is formed, and a layer having a lower refractive index than that of the layer (SWS 11). It is possible to form a state in which a portion that is formed only by the protective layer 20 is formed. As a result, the reflectance of the optical member 1 can be further reduced as compared with the case where the SWS 11 is formed on the surface 10 a and the protective film 20 is not formed, or the case where only the protective film 20 is formed without forming the SWS 11.

  Further, the protective film 20 has a thickness such that the phase of the reflected light on the surface 20a of the protective film 20 and the phase of the reflected light on the surface 10a of the optical member body 10 are shifted by half the wavelength of the incident light. Is preferred. Specifically, the substantial optical path difference between the reflected light on the surface 10a of the optical member body 10 and the reflected light on the surface 20a of the protective film 20 is shifted by 1/2 of the wavelength of the incident light. It is preferable to set so. By doing so, the reflected light on the surface 20a of the protective film 20 and the reflected light on the surface 10a of the optical member body 10 can be interfered and weakened. As a result, the reflectance of the optical member 1 can be further reduced. In this case, it is particularly preferable that the intensity of the reflected light generated on the surface 10a of the optical member body 10 is substantially equal to the intensity of the reflected light generated on the surface 20a of the protective film 20 by changing the shape of the antireflection concavo-convex structure 11. preferable. By doing so, it is possible to prevent substantially no reflected light. That is, a non-reflective structure can be realized.

  Further, by adjusting the film thickness of the protective film 20, it is possible to selectively reduce the reflectance at a certain wavelength or to reduce the wavelength dependency.

  Hereinafter, the specific configuration of the optical member 1 according to the first embodiment will be described in more detail with reference to FIGS. 1 and 2.

In the first embodiment, the optical member body 10 is substantially made of glass, and an antireflection concavo-convex structure 11 is formed on the surface 10a thereof. The antireflection concavo-convex structure 11 includes a plurality of columnar convex portions 12 regularly arranged. More specifically, in the first embodiment, the plurality of convex portions 12 have a period (less than the wavelength of the incident light (specifically, the shortest wavelength of the incident light when the incident light is not a single wavelength)) ( They are arranged in a matrix (square arrangement) spaced apart from each other by (pitch) Λ. The height t ₁ of the convex portion 12 is 0.4 times or more of the wavelength of the incident light (specifically, when the incident light is not light of a single wavelength, 0.4 times or more of the longest wavelength of the incident light) ) Is set. For this reason, a layer whose refractive index gradually changes is formed on the surface portion of the surface 10a, and reflection of incident light incident on the surface 10a via the protective film 20 is effectively suppressed.

  In addition, even if it is a case where the convex part 12 is columnar like this Embodiment 1, the effective refractive index of the surface layer part in which the convex part 12 exists can be reduced by providing the convex part 12. FIG. Therefore, the reflection of incident light can be effectively reduced.

  On this surface 10a, a protective film 20 substantially made of a resin is formed so as to cover the surface 10a. Specifically, in the first embodiment, the protective film 20 fills the concave portions between the plurality of convex portions 12 arranged, and the surface 20a opposite to the optical member body 10 side of the protective film 20 is a smooth surface (unevenness). A smooth surface or the like in the first embodiment. For this reason, the convex part 12 is protected from the impact and vibration from the outside by this protective film 20, and the deformation | transformation and damage of the convex part 12 are suppressed effectively. Therefore, high mechanical durability can be realized.

  By the way, in general, glass has low chemical durability (water resistance and acid resistance), and when the glass material is exposed, white burn or blue burn is generated. On the other hand, since resin has higher chemical durability than glass, chemical modification of optical member main body 10 substantially made of glass is achieved by covering optical member 10 with protective film 20 made substantially of resin. (Discoloration etc.) can be effectively suppressed.

  In the first embodiment, the protective film 20 has a refractive index at a wavelength of incident light lower than that of the optical member body 10. For this reason, it will be in the state where two layers whose refractive index is lower than optical member main part 10 are laminated on surface 10a of optical member main part 10 as mentioned above. Therefore, the reflectance of the optical member 1 can be effectively reduced.

Distance from the top of the convex portion 12 to the surface 20a (in this specification, thickness and defining this distance protective membrane 20) t ₂ is the reflectance of the optical member 1, the wavelength of the reflectance of the optical member 1 Correlate with both dependencies. For example, the incident light may be light of a single wavelength, the thickness t ₂ of the protective layer 20, the reflected light generated on the surface 10a of the optical member body 10 phase and the reflected light generated by the surface 20a of the protective film 20 By setting the difference from the phase to be half (1/2) the wavelength of the incident light, the reflected light generated on the surface 10a and the reflected light generated on the surface 20a can be interfered and weakened. Therefore, by setting the thickness t ₂ of such protection film 20, it is possible to reduce the reflectance of the optical member 1 for incident light of a certain wavelength more effectively. In this case, the height t ₁ of the convex portion 12, and particularly preferably the intensity of the reflected light generated by the reflection light intensity and the surface 20a occurring at the surface 10a such that substantially equal. By doing so, it becomes possible to make the reflectance of the optical member 1 substantially zero.

However, if you set the thickness t ₂ of such protection film 20, resulting in the surface 20a of the phase and the protective film 20 of the reflected light generated on the surface 10a of the optical member body 10 with respect to incident light of another wavelength Since the difference from the phase of the reflected light does not become half (1/2) of the wavelength of the incident light, the wavelength dependence of the reflectance of the optical member 1 becomes relatively large.

Hereinafter, by changing the conditions of the film thickness t _2, etc. of the protective film 20, more specifically described by way of a specific example that it is possible to change the reflectance and the wavelength dependence of the optical member 1.

FIG. 3 shows a period Λ: 300 nm, a refractive index of the optical member body 10 at a wavelength of 589 nm: 2.00136, a refractive index of the protective film 20 at a wavelength of 589 nm: 1.37986, t ₁ : 150 nm, t ₂ : 110 nm, a convex portion. 12 is a graph showing the correlation between the reflectance of the optical member 1 with respect to incident light with an incident angle of 0 ° and the wavelength of incident light when the diameter f of the top of 12 is 90.5 nm. The dispersion of the protective film 20 is defined by the following mathematical formula (1). Further, the dispersion of the optical member body 10 is defined by the following mathematical formula (2).
n ² −1 = K ₁ λ ² / (λ ² −L ₁ ) + K ₂ λ ² / (λ ² −L ₂ ) + K ₃ λ ² / (λ ² −L ₃ ) (1)
However,
K ₁ = 0.487555108,
K ₂ = 0.398775031,
K ₃ = 2.3120353,
L ₁ = 0.00600069867,
L ₂ = 0.00895188847,
L ₃ = 566.135559,
It is.
n ² = a ₀ + a ₁ λ ² ++ a ₂ λ ⁻² + a ₃ λ ⁻⁴ + a ₄ λ ⁻⁶ + a ₅ λ ⁻⁸ (2)
However,
a ₀ = 3.778725,
a ₁ = −0.020974414,
a ₂ = 0.0592558017,
a ₃ = 0.0079700797,
a ₄ = −0.00070884578,
a ₅ = 7.9345324e-005,
It is.

  FIG. 4 is a graph showing the correlation between the incident angle of incident light (wavelength: 589 nm) and the reflectance under the same conditions as in FIG.

FIG. 5 shows a period Λ: 300 nm, a refractive index of the optical member body 10 at a wavelength of 589 nm: 2.00136, a refractive index of the protective film 20 at a wavelength of 589 nm: 1.37986, t ₁ : 150 nm, t ₂ : 140 nm, a convex portion. 12 is a graph showing the correlation between the reflectance of the optical member 1 with respect to incident light with an incident angle of 0 ° and the wavelength of incident light when the diameter f of the top of 12 is 135 nm. The dispersion of the protective film 20 is defined by the above mathematical formula (1). Further, the dispersion of the optical member body 10 is defined by the above mathematical formula (2).

  FIG. 6 is a graph showing the correlation between the incident angle of incident light (wavelength: 589 nm) and the reflectance under the same conditions as in FIG.

3 to 6, A indicates the reflectance of the optical member 1 of the first embodiment. B shows the reflectance when the SWS 11 is not provided and the protective film 20 is formed on the flat surface 10a. C indicates the reflectance when the protective film 20 is not provided. Also, D is, without providing the protective film 20, and shows the reflectance in the case of half the height t ₁ of the convex portion 12.

  Here, the conditions of the graph (A) shown in FIGS. 3 and 4 are the phase of the reflected light generated on the surface 10a of the optical member body 10 and the surface 20a of the protective film 20 when incident light having a wavelength of 589 nm is incident. The difference from the phase of the generated reflected light is half (1/2) the wavelength of the incident light, and the intensity of the reflected light generated on the surface 10a and the reflected light generated on the surface 20a in that case is substantially the same. It is a condition. By setting such conditions, as shown in FIGS. 3 and 4, reflection of vertical incident light having a wavelength of 589 nm (incident light having an incident angle of 0 °) can be suppressed almost completely.

  In addition, as shown in FIG. 4, by providing the protective film 20, it is possible to effectively suppress the reflection of incident light having a particularly small incident angle, compared to the case where the protective film 20 is not provided (C, D). . However, as shown in FIG. 3, the wavelength dependency of the reflectance tends to be larger than when the protective film 20 is not provided (in the case of C or D).

  On the other hand, under the conditions of the graph (A) shown in FIGS. 5 and 6, unlike the case shown in FIG. 3 and the like, the reflectance of the optical member 1 is substantially zero as shown in FIG. Although no particular wavelength appears, the wavelength dependence of the reflectance can be further reduced. 5 and 6 that the wavelength dependency of the reflectance can be further reduced as compared with the case where the protective film 20 is not provided.

  As described above, in the first embodiment, an example of a preferable embodiment in which the present invention is implemented is described by taking the case where the optical member main body 10 transmits incident light as an example, but the present invention is limited to this configuration. It is not a thing. For example, the optical member body 10 may be a so-called black body that absorbs incident light. Even in that case, the environmental resistance can be improved by providing the protective film 20. In addition, the light reflectance can be more effectively reduced.

  In the first embodiment, the example in which the convex portions 12 are squarely arranged in a matrix has been described. However, the arrangement of the convex portions 12 is not particularly limited to this. For example, a triangular lattice shape (delta shape) ) May be arranged. The arrangement of the protrusions 12 is not particularly limited as long as a gentle refractive index change occurs in the surface layer portion where the protrusions 12 (antireflection uneven structure 11) are formed.

  In the first embodiment, the optical member 1 on which the surface on which the SWS 11 is formed is a flat surface has been described as an example. However, as shown in the following embodiment, the shape of the surface on which the SWS 11 is provided is particularly limited. The shape of the optical member according to the present invention is not particularly limited.

(Modification 1)
FIG. 7 is a cross-sectional view of the optical member 2 according to the first modification.

  The optical member 2 according to Modification 1 has the same configuration except for the configuration of the optical member 1 according to Embodiment 1 and the protective film 20. Here, the configuration of the protective film 20 in Modification 1 will be described in detail. In the description of the first modification, components having substantially the same function will be described with reference numerals common to the first embodiment, and description thereof will be omitted.

  In the first embodiment, the protective film 20 is relatively thick and fills the concave portions formed between the plurality of convex portions 12 and is formed so that the surface 20a becomes a smooth surface (for example, a smooth surface). Has been. However, the present invention is not limited to this configuration. For example, as in Modification 2, the protective film 20 may be relatively thin and formed in a shape along the antireflection uneven structure 11. . That is, unevenness corresponding to the antireflection uneven structure 11 may be formed on the surface 20a. Even in this case, high chemical durability can be realized as in the case of the first embodiment. Further, higher mechanical durability can be realized than when the protective film 20 is not provided.

  Further, as in the case of Example 1 described above, the layer thickness of the protective film 20 and the shape of the projections 12 are appropriately adjusted to further reduce the reflectance and reduce the wavelength dependence of the reflectance. Can be planned.

(Embodiment 2)
FIG. 8 is a plan view of the optical member 3 according to the second embodiment.

  FIG. 9 is a cross-sectional view of a portion cut out by a cut line IX-IX in FIG.

  The optical member 3 according to Embodiment 2 has the same configuration except for the shape of the optical member 1 according to Embodiment 1 and the antireflection uneven structure 11. Here, the shape of the antireflection concavo-convex structure 11 in Embodiment 2 will be described in detail. In the description of the second embodiment, components having substantially the same function are described with reference numerals common to the first embodiment, and the description thereof is omitted.

  As shown in FIGS. 8 and 9, in the second embodiment, the antireflection concavo-convex structure (SWS) 11 is constituted by a plurality of dome-shaped convex portions 12 arranged densely in a matrix. As in the second embodiment, the antireflection concavo-convex structure 11 is configured by the plurality of dome-shaped convex portions 12, so that the antireflection concavo-convex structure 11 is configured by the plurality of columnar convex portions 12 in the surface layer portion. The refractive index change can be made smoother. Further, incident light is irregularly reflected on the surface 10a. Therefore, the reflectance at the surface 10a can be further reduced.

  Moreover, the wavelength dependence of the reflectance of the optical member 3 can be further reduced. Furthermore, the incident angle dependency of the reflectance of the optical member 3 can be further reduced, and a high reflection suppressing effect can be realized even for incident light having a relatively large incident angle.

  In the second embodiment, the reflectance on the surface 10a of the optical member body 10 correlates with the height of the convex portion 12 formed on the surface 10a. Specifically, the reflectance decreases as the height of the convex portion 12 increases, and conversely, the reflectance tends to increase as the height of the convex portion 12 decreases. As described above, by providing the protective film 20 made of a low refractive index material, the reflectivity of the optical member 3 (“reflectance of the optical member” is emitted from the surface 20a with respect to the intensity of light incident on the surface 10a. The intensity of the reflected light (which is the intensity of the combined reflected light generated on the surface 10a and the reflected light generated on the surface 20a) can be reduced. It is possible to achieve a desired low reflectance even when the value is lowered. That is, by providing the protective film 20, the height of the convex portion 12 can be made relatively low, and the optical member 3 can be easily manufactured.

  Hereinafter, the reflection suppression effect of the optical member 3 according to the second embodiment will be specifically described with reference to further specific examples.

In FIG. 10, the period Λ: 300 nm, the refractive index of the optical member body 10 at a wavelength of 589 nm: 1.51674, the refractive index of the protective film 20 at a wavelength of 589 nm: 1.10000, t ₁ : 150 nm, t ₂ : 40 nm, convex FIG. 7 is a graph showing the correlation between the reflectance of the optical member 3 and the wavelength of incident light with respect to incident light with an incident angle of 0 ° when the shape of the portion 12 is set to conform to y = −ax ² (a is an arbitrary constant). is there. However, the y axis extends in the normal direction of the base surface of the surface 10a, and the x axis extends in a direction perpendicular to the y axis in a cross section passing through the center of the convex portion 12. Further, the wavelength dependency of the refractive index of the protective film 20 is not assumed.

  FIG. 11 is a graph showing the correlation between the incident angle of incident light (wavelength: 589 nm) and the reflectance under the same conditions as in FIG.

10 and 11, A indicates the reflectance of the optical member 3 of the second embodiment. B shows the reflectance when the SWS 11 is not provided and the protective film 20 is formed on the flat surface 10a. C indicates the reflectance when the protective film 20 is not provided. Also, D is, without providing the protective film 20, and shows the reflectance in the case of half the height t ₁ of the convex portion 12.

  As shown in FIG. 10, the reflectance of the optical member 3 and its wavelength dependency can be more effectively reduced by adopting the configuration of the second embodiment. Moreover, as shown in FIG. 11, the incident angle dependence of the reflectance of the optical member 3 can be further reduced, and the reflectance for incident light having a relatively large incident angle can also be effectively reduced.

(Modification 2)
FIG. 12 is a cross-sectional view of the optical member 4 according to the second modification.

FIG. 13 shows a period Λ: 300 nm, a refractive index of the optical member body 10 at a wavelength of 589 nm: 2.00136, a refractive index of the protective film 20 at a wavelength of 589 nm: 1.49169, t ₁ : 300 nm, t ₂ : 89 nm, t _3. : 243 nm, the reflectance of the optical member 4 with respect to the incident light with an incident angle of 0 ° and the wavelength of the incident light when the shape of the convex portion 12 is along y = −ax ² (a is an arbitrary constant) It is a graph showing a correlation. The dispersion of the protective film 20 is defined by the following mathematical formula (3). Further, the dispersion of the optical member body 10 is defined by the following mathematical formula (4).
n ² = a ₀ + a ₁ λ ² +++ a ₂ λ ⁻² + a ₃ λ ⁻⁴ + a ₄ λ ⁻⁶ + a ₅ λ ⁻⁸ (3)
However,
a ₀ = 2.1864582,
a ₁ = −0.00024475348,
a ₂ = 0.0145155787,
a ₃ = −0.000443297981,
a ₄ = 7.7664259e-005,
a ₅ = −2.9936382e-006,
It is.
n ² = a ₀ + a ₁ λ ² ++ a ₂ λ ⁻² + a ₃ λ ⁻⁴ + a ₄ λ ⁻⁶ + a ₅ λ ⁻⁸ (4)
However,
a ₀ = 3.778725,
a ₁ = −0.020974414,
a ₂ = 0.0592558017,
a ₃ = 0.0079700797,
a ₄ = −0.00070884578,
a ₅ = 7.9345324e-005,
It is.

  FIG. 14 is a graph showing the correlation between the incident angle of incident light (wavelength: 589 nm) and the reflectance under the same conditions as in FIG.

In FIGS. 13 and 14, A represents the reflectance of the optical member 4 of the second modification. B shows the reflectance when the SWS 11 is not provided and the protective film 20 is formed on the flat surface 10a. C indicates the reflectance when the protective film 20 is not provided. Also, D is, without providing the protective film 20, and indicates the reflectance in the case of half the height t ₁ of the convex portion 12.

  The optical member 4 according to the second modification has the same configuration except for the configuration of the optical member 3 and the protective film 20 according to the second embodiment. Here, the configuration of the protective film 20 in Modification 2 will be described in detail. In the description of the second modification, components having substantially the same function will be described with reference numerals common to the first and second embodiments, and description thereof will be omitted.

  In the second embodiment, the protective film 20 is relatively thick and fills the concave portions formed between the plurality of convex portions 12 and is formed so that the surface 20a becomes a smooth surface (for example, a smooth surface). Has been. However, the present invention is not limited to this configuration. For example, as in Modification 2, the protective film 20 may be relatively thin and formed in a shape along the antireflection uneven structure 11. . That is, unevenness corresponding to the antireflection uneven structure 11 may be formed on the surface 20a. Even in this case, high chemical durability can be realized as in the case of the second embodiment. Further, higher mechanical durability can be realized than when the protective film 20 is not provided.

  Further, as shown in FIGS. 13 and 14, as in the case of the first embodiment, the reflectance can be further effectively reduced by appropriately adjusting the layer thickness of the protective film 20 and the shape of the convex portion 12. In addition, the wavelength dependence of the reflectance can be reduced.

  Next, an optical device using the optical member embodying the present invention will be described by taking Embodiments 3 and 4 as examples.

(Embodiment 3)
FIG. 15 is a diagram illustrating a configuration of a main part of the imaging device 5 according to the third embodiment.

  As illustrated in FIG. 15, the imaging apparatus 5 according to the third embodiment includes an apparatus main body 33, a lens barrel unit 30, and an imaging element 34. The lens barrel unit 30 includes a cylindrical (specifically cylindrical) lens barrel 31 and an imaging optical system 32 housed inside the lens barrel 31. The imaging optical system 32 is for imaging light incident on the lens barrel 31 from the image side (left side in FIG. 15). In the third embodiment, the imaging optical system 32 is specifically configured by a first lens 32a, a second lens 32b, and a third lens 32c. The lenses 32a to 32c constituting the imaging optical system 32 may be disposed on the optical axis so as not to be displaced. In addition, at least one of the lenses 32a to 32c is configured to be displaceable on the optical axis, and may be configured to be capable of focusing and zooming.

  The lens barrel unit 30 is attached to the apparatus main body 33. The lens barrel unit 30 may be detachable from the apparatus main body 33 or may be attached to the apparatus main body 33 so as not to be detached.

  The device body 33 is provided with an image sensor 34. The image sensor 34 is disposed on the optical axis of the imaging optical system 32. Specifically, the imaging element 34 has an imaging surface, and is arranged so that an optical image is formed on the imaging surface by the imaging optical system 32. The image sensor 34 has a function as a photodetector. Specifically, the image sensor 34 has a function of detecting an optical image formed on the optical image and outputting an electrical signal corresponding to the optical image. The image sensor 34 can be configured by, for example, a charge coupled device (CCD), a complementary metal-oxide semiconductor (COMS), or the like.

  In the third embodiment, the electrical signal output from the image sensor 34 is configured to be input and recorded in a recording device (not shown) (for example, a hard disk) housed in the apparatus main body 33.

  FIG. 16 is a perspective view of the lens barrel 31.

  FIG. 17 is an enlarged sectional view of a part of the lens barrel 31.

  In principle, the imaging optical system 32 is designed so that light incident on the imaging optical system 32 is imaged on the imaging surface of the imaging element 34. However, a part of the light incident on the imaging optical system 32, such as light having a maximum angle of view of the imaging optical system 32, is not directly imaged on the image sensor 34 but is incident on the inner peripheral surface of the lens barrel 31. Will be. For this reason, when the light reflectance of the inner peripheral surface of the lens barrel 31 is high, reflected light (stray light) is generated on the inner peripheral surface, which may cause ghost or flare.

  In the third embodiment, the lens barrel 31 includes a barrel main body 35 formed in a cylindrical shape and a protective film 38 that is formed so as to cover the inner peripheral surface of the barrel main body 35 and transmits visible light. It is comprised by. An antireflection concavo-convex structure (so-called SWS) 36 is formed over the entire inner peripheral surface of the lens barrel body 35. The antireflection concavo-convex structure 36 is formed by regularly arranging a plurality of fine linear protrusions 37 extending in parallel with each other in the extending direction of the lens barrel 31 along the circumferential surface. Specifically, the plurality of linear protrusions 37 are arranged at a pitch (pitch: distance between the apexes between adjacent linear protrusions 37) that is equal to or less than the wavelength of the light from the imaging optical system 32. Specifically, for example, when visible light (light having a wavelength of 400 nm or more and 700 nm or less) is incident on the imaging optical system 32, light (for example, the imaging element 34 has a wavelength of 450 nm) that suppresses reflection among the incident light. In the case where the following light is not detected, the light can be 450 nm or more), and the light is arranged at a pitch equal to or shorter than the wavelength of the shortest light.

  The lens barrel body 35 is configured to absorb light from the imaging optical system 32. Specifically, the lens barrel main body 35 is configured to include a light absorbing material (for example, a black dye or a black pigment). For this reason, the reflection of the incident light on the inner peripheral surface is effectively suppressed, and the incident light on the lens barrel 31 is absorbed by the barrel main body 35 with a high absorption rate. Therefore, generation of stray light due to reflected light or the like on the inner peripheral surface can be suppressed. As a result, the occurrence of ghosts and flares can be effectively suppressed, and the imaging device 5 having high optical performance can be realized.

  In the third embodiment, as shown in FIG. 17, the protective film 38 is formed on the antireflection concavo-convex structure 36 so as to cover the antireflection concavo-convex structure 36. As described above, high environmental resistance can be realized. Further, since the refractive index distribution can be made gentler in the surface layer portion near the inner peripheral surface of the lens barrel 31, the generation of reflected light in the lens barrel 31 can be more effectively suppressed. Therefore, higher optical performance of the imaging device 5 can be realized.

  In addition, it is preferable to form the inner peripheral surface of the lens barrel 31 on which the SWS 36 is formed as a rough surface from the viewpoint of realizing higher optical performance. By doing so, the incidence angle dependence of the reflectance on the inner peripheral surface can be further reduced, and the regular reflection component can be more effectively reduced.

(Embodiment 4)
FIG. 18 is a diagram illustrating a configuration of a main part of the optical pickup device 6 according to the fourth embodiment.

  FIG. 19 is a cross-sectional view of the objective lens 46.

  The optical pickup device 6 according to the fourth embodiment focuses information on the information recording surface 47a of an information recording medium (for example, an optical disc) 47 and detects reflected light on the information recording surface 47a to record information. The information recorded on the surface 47a can be read out.

  The optical pickup device 6 includes a laser light source 41, a collimator 42, a beam splitter 43, an objective lens 46 constituting an objective optical system, and a detector 45. The collimator 42 has a function of converting laser light emitted from the laser light source 41 into parallel light. The laser light converted into parallel light by the collimator 42 passes through the beam splitter 43 and enters the objective lens 46. The objective lens 46 is for focusing the laser beam on the information recording surface 47a of the information recording medium 47 provided with the laser beam. The laser beam focused by the objective lens 46 is reflected by the information recording surface 47a. The reflected light passes through the objective lens 46 and enters the beam splitter 43. The light is reflected by the reflecting surface provided on the beam splitter 43 and the reflected light is guided to the detector 45. The reflected light is detected by the detector 45, and data is read based on the detected reflected light.

  In the fourth embodiment, an example of the present invention will be described by taking an optical pickup device 6 of a type that focuses laser light on one type of information recording medium 47 as an example. A so-called compatible type capable of focusing laser light on each of the recording media 47 may be used.

  Incidentally, as described above, the laser light incident on the objective lens 46 passes through the objective lens 46. However, if antireflection processing is not performed on both lens surfaces of the objective lens 46, a part of the laser light is reflected on both lens surfaces of the objective lens 46. If a part of the laser beam is reflected on both lens surfaces of the objective lens 46, the amount of the laser beam detected by the detector 45 is decreased, so that the detection accuracy tends to be decreased. As a result, noise or the like may occur.

  In the fourth embodiment, the objective lens 46 includes a lens body 48 and protective films 51 a and 51 b provided on the lens surfaces of the lens body 48 so as to cover the lens surfaces. An antireflection concavo-convex structure 49 in which a plurality of fine cone-shaped convex portions 50 are regularly arranged is formed at least within the effective optical diameter of the lens surface 48a on the laser light source 41 side of the lens body 48. . Specifically, the plurality of cone-shaped convex portions 50 are arranged at a pitch (the distance between the apexes between the cone-shaped convex portions 50 located closest to each other) that is equal to or less than the wavelength of the laser light emitted from the laser light source 41. (For example, a square arrangement or a triangular lattice arrangement).

  Further, an antireflection concavo-convex structure 49 in which a plurality of fine cone-shaped convex portions 50 are regularly arranged is formed at least within the effective optical diameter of the lens surface 48b on the information recording medium 47 side of the lens body 48. Yes. Specifically, the plurality of cone-shaped convex portions 50 are arranged at a pitch (the distance between the apexes between the cone-shaped convex portions 50 located closest to each other) that is equal to or less than the wavelength of the laser light emitted from the laser light source 41. (For example, a square arrangement or a triangular lattice arrangement).

  For this reason, the reflection of the laser beam on both lens surfaces of the objective lens 46 can be suppressed. As a result, the amount of laser light detected by the detector 45 can be made relatively large, and the generation of noise can be effectively suppressed. Therefore, the optical pickup device 6 having high optical performance can be realized.

  In the fourth embodiment, protective films 51 a and 51 b are formed on each lens surface of the lens body 48 so as to cover the antireflection uneven structure 49. For this reason, as demonstrated in the said Embodiment 1, high environmental resistance and a higher reflection suppression effect are realizable. Therefore, the optical pickup device 6 having higher optical performance can be realized.

  As long as the pitch of the antireflection concavo-convex structure 49 is equal to or less than the wavelength of the laser beam within at least the optical effective diameter of the lens surfaces 48a and 46b, the pitch of the antireflection concavo-convex structure 49 is within the optical effective diameter of the lens surfaces 48a and 46b. May be substantially constant (i.e., may be periodic). In addition, the pitch of the antireflection concavo-convex structure 49 may be different from each other at various locations within the optical effective diameter. That is, the antireflection uneven structure 49 may be aperiodic. Generation of diffracted light on the lens surfaces 48a and 46b can be effectively suppressed by making the antireflection uneven structure 49 non-periodic.

  As described above, in the third and fourth embodiments, the imaging device and the optical pickup device have been described as examples of the optical device including the optical member according to the present invention. However, the present invention is not limited to the optical scanning device or the like. The present invention can also be applied to various optical devices.

  The optical member according to the present invention has an antireflection effect and high environmental resistance, and is useful as a lens barrel, an optical element represented by a lens, and the like. By using the optical member according to the present invention, various optical systems such as a high-quality imaging optical system, objective optical system, scanning optical system, and pickup optical system, lens barrel unit, optical pickup unit, and imaging unit An optical unit, an imaging device, an optical pickup device, an optical scanning device, and the like can be realized.

FIG. 1 is a plan view of an optical member (antireflection structure) 1 according to the first embodiment. FIG. 2 is a cross-sectional view of a portion cut out along a cut line II-II in FIG. FIG. 3 shows a period Λ: 300 nm, a refractive index of the optical member body 10 at a wavelength of 589 nm: 2.00136, a refractive index of the protective film 20 at a wavelength of 589 nm: 1.37986, t ₁ : 150 nm, t ₂ : 110 nm, a convex portion. 12 is a graph showing the correlation between the reflectance of the optical member 1 with respect to incident light with an incident angle of 0 ° and the wavelength of incident light when the diameter f of the top of 12 is 90.5 nm. FIG. 4 is a graph showing the correlation between the incident angle of incident light (wavelength: 589 nm) and the reflectance under the same conditions as in FIG. FIG. 5 shows a period Λ: 300 nm, a refractive index of the optical member body 10 at a wavelength of 589 nm: 2.00136, a refractive index of the protective film 20 at a wavelength of 589 nm: 1.37986, t ₁ : 150 nm, t ₂ : 140 nm, a convex portion. 12 is a graph showing the correlation between the reflectance of the optical member 1 with respect to incident light with an incident angle of 0 ° and the wavelength of incident light when the diameter f of the top of 12 is 135 nm. FIG. 6 is a graph showing the correlation between the incident angle of incident light (wavelength: 589 nm) and the reflectance under the same conditions as in FIG. FIG. 7 is a cross-sectional view of the optical member 2 according to the first modification. FIG. 8 is a plan view of the optical member 3 according to the second embodiment. FIG. 9 is a cross-sectional view of a portion cut out by a cut line IX-IX in FIG. In FIG. 10, the period Λ: 300 nm, the refractive index of the optical member body 10 at a wavelength of 589 nm: 1.51674, the refractive index of the protective film 20 at a wavelength of 589 nm: 1.10000, t ₁ : 150 nm, t ₂ : 40 nm, convex FIG. 7 is a graph showing the correlation between the reflectance of the optical member 3 and the wavelength of incident light with respect to incident light with an incident angle of 0 ° when the shape of the portion 12 is set to conform to y = −ax ² (a is an arbitrary constant). is there. FIG. 11 is a graph showing the correlation between the incident angle of incident light (wavelength: 589 nm) and the reflectance under the same conditions as in FIG. FIG. 12 is a cross-sectional view of the optical member 4 according to the second modification. FIG. 13 shows a period Λ: 300 nm, a refractive index of the optical member body 10 at a wavelength of 589 nm: 2.00136, a refractive index of the protective film 20 at a wavelength of 589 nm: 1.49169, t ₁ : 300 nm, t ₂ : 89 nm, t _3. : 243 nm, the reflectance of the optical member 4 with respect to the incident light with an incident angle of 0 ° and the wavelength of the incident light when the shape of the convex portion 12 is along y = −ax ² (a is an arbitrary constant) It is a graph showing a correlation. FIG. 14 is a graph showing the correlation between the incident angle of incident light (wavelength: 589 nm) and the reflectance under the same conditions as in FIG. FIG. 15 is a diagram illustrating a configuration of a main part of the imaging device 5 according to the third embodiment. FIG. 16 is a perspective view of the lens barrel 31. FIG. 17 is an enlarged cross-sectional view of a part of the lens barrel 31. FIG. 18 is a diagram illustrating a configuration of a main part of the optical pickup device 6 according to the fourth embodiment. FIG. 19 is a cross-sectional view of the objective lens 46.

Explanation of symbols

1, 2, 3, 4 Optical member 5 Imaging device 6 Optical pickup device 10 Optical member body 11, 36, 49 Anti-reflection concavo-convex structure (SWS)
DESCRIPTION OF SYMBOLS 12 Convex part 20,38,51a, 51b Protective film 30 Lens barrel unit 31 Lens barrel 32 Imaging optical system 33 Apparatus main body 34 Imaging element 35 Lens barrel main body 37 Linear convex part 41 Laser light source 42 Collimator 43 Beam splitter 45 Detector 46 Objective lens 47 Information recording medium 47a Information recording surface 48 Lens body 50 Conical convex portion

Claims (10)

An optical member body in which a plurality of fine convex portions or concave portions are arranged, and an antireflection uneven structure that suppresses reflection of incident light is formed on the surface;
A protective film covering the surface and transmitting the incident light;
An optical member comprising: The optical member according to claim 1,
The optical member main body is substantially made of glass, while the protective film is substantially made of resin. The optical member according to claim 1,
The optical member, wherein the protective film has higher chemical durability than the optical member body. The optical member according to claim 1,
The optical member main body transmits the incident light, and the refractive index of the protective film at the wavelength of the incident light is lower than the same refractive index of the optical member main body. The optical member according to claim 1,
An optical member in which the surface of the protective film is formed on a smooth surface. The optical member according to claim 1,
An optical member, wherein the surface of the protective film is provided with unevenness corresponding to the antireflection uneven structure. The optical member according to claim 1,
The protective film is formed to have such a thickness that the phase of the reflected light on the surface of the protective film and the phase of the reflected light on the surface of the optical member body are shifted by half the wavelength of the incident light. Optical member to be used. The optical member according to claim 7,
The antireflection uneven structure is formed such that the intensity of reflected light on the surface of the optical member body and the intensity of reflected light on the surface of the protective film are substantially equal to each other. Element. The optical member according to claim 1,
The antireflection concavo-convex structure includes a plurality of linear protrusions or recesses arranged in parallel to each other, a plurality of cone-shaped protrusions or recesses arranged, a frustum-like protrusion or recess An optical member characterized in that a plurality of slabs are arranged, or a plurality of columnar projections or recesses are arranged.   An optical device comprising the optical member according to claim 1.

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